Following injury, articular cartilage either fails to repair completely or repairs in such a manner that it loses its former biochemical and biomecha- nical characteristics-a problem that present treatment modalities are inadequate in addressing. Previous reports by this group and others have demonstrated the viability of using chondrocyte transplants to heal lesions in articular cartilage. While these reports are encouraging, there remains the need to improve the efficacy and reproducibility of such a procedure. The course of research detailed herein focuses on the use of a collagen- chondrocyte composite to immobilize chondrocytes within a matrix and thus maintain their location within a cartilage defect. The proposed work will utilize in vitro and in vivo pilot experiments to investigate the viability of a tissue analogue consisting of a collagen matrix and cultured chondroc- ytes. Initial experimentation will define the various parameters of cellular ingrowth and metabolism in collagen matrices having different pore sizes. These samples will be evaluated histologically, biochemically, and autoradiographically. The second phase of this work will evaluate tissue repair properties of the tissue analogue in vivo for the purpose of healing cartilage lesions. Samples will be evaluated histologically, biochemically, autoradiographi- cally, and biomechanically.